Aircraft wheel control device



Aug. 75 1945. 'F. N. SCHWEND AIRCRAFT WHEEL CONTROL DEVICE Filed Sept. 16,-1943 Sheets-Sheet 1 Aug. 7, 1945. F. N. SCHWEND AIRCRAFT WHEEL CONTROL DEVICE Fiied Sept. '16, 1943 4 Sheets-Shet 2 Aug. 7, 1945.-. v F.- N.-'S CHWEND 2,381,842

AIRCRAFT WHEEL CONTROL DEVICE Filed Sept. 16, 1945 4 Sheets-Sheeii s \J" v M FIEAL- A I l N VEN TOR:

F N. SCHWEND AIRCRAFT WHEEL CONTROL DEVICE Filed Sept. '16; 19 43 4 Sheets-Sheet 4 ZJ WINVQITORT and is taken along the line 8-6 of Fig. 5.

Patented Aug. 7, 1945 UNITED STATES PATENT OFFICE mom war-zen con'rnor. DEVICE Fred -N. Schwend, Berkeley, Calif. I Application September 16, 1948, Serial No. 502,615 11 Claims. ((1244-1133) The present invention relates to aircraft wheel driving and braking mechanism and has particular reference to controls for aircraft landing wheels.

As is well known. the wheels of airplanes, par"- ticularly if they are relatively heavy, are subject to considerable skidding when they. first touch the ground in landing and this. tends to reduce the life of the landing wheel tires as well as to increase the'possibility of damage upon landing.

Further, and especially with aircraft of considerable size, difficulty has been encountered in dissipating the heat generated by the usual friction type brakes, this heat at times damaging the tires and wheels as well as requiring frequent, replacement of the parts.

The present invention is aimed at overcoming the above and other shortcomings and one object is to rotate the landing wheels of an aircraft prior to and as an incident to landing.

Another object is to automatically control'a wheel spinning device and to obviate the neces-,

'sity of attention thereto by the operator.

A further object is to.spin the landing wheels of an aircraft at a speed commensurate with the landing speed of the craft.

A further object is to eliminate high-pressure fluid brake lines inherent in conventional hydraulic brakes. I A further object is to provide a unitary brake and wheel spinning device.

The manner in which objects of the invention are accomplished iwill be readily understood on reference to the following specification when read in conjunction with the accompanying drawings wherein:

Fig. 1 is aside view of a retractable and extensible landing gear combined with the present invention.

Fig. 2 is a schematicperspective view of the 1 hydraulic controls embodying the present invention.

Fig. 3 is a sectional view of one of the fluid motor-brake units and is taken along the line 3-4 of Fig.4.

a Fig. 4 is a transverse sectional view taken along the line 4-4 of Fig. 3.

Fig. 5 isan outside viewof a motor-brake unit and illustrating the brake control valve cyl- -inder partly in section.

' Fig. 6 is a transverse-view of the control valve the above and other only spinning control applied to landing wheels incorporating the conventional formof friction "brakes.

Referring to the drawings, the landing wheels,

of which is shown at Ii (Fig. 1), are retractable within the hull [2 of the aircraft. Since 0 mechanism for retracting f aiid extending the landing wheels is well known in the art and since such mechanism enters into' cooperative relationship with other parts of the present invention, a brief description of such mechanism will be given to indicate the relationship thereof with the component parts of the control mechanism for the motor-brake unit.

The wheels H are attached to the well known,

form of oleo" shockjabsorbingunit comprising, for each wheel, a pair of telescoping pistons l3 and cylinders it, the former rigidly secured to the shaft ii of the respective landing wheel in the manner shown, for example, in Fig. '4, and the latter pivoted on a pin it fixed to the framework of the aircraft.

Each wheel is movable from its extended position illustrated in full lines or in dotted lines ilb (Fig. l) to its dotted line position Ha. with-' in the hull l2 by a hydraulic cylinder II pivoted at 20 to the framework of the aircraft and having the rod of the piston'l8 thereof pivotally connected at I9 to the cylinder I4,

Retraction and extension of the landing wheels is controlled by a handle 2| attached to a twoway valve schematically indicated at 2-2, and when the handle is moved from its full line positionto its dotted line position the wheels will be retracted and held retracted while movement in an opposite manner will effect extension of the wheels. When the handle is in its position illustrated in Fig. 1, the valve 22 connects a hydraulic tube or line 23 leading from the usual landing gear pressure supply pump to a line 26 connected in parallelto the lower end of a latch release cylinder 28 and a sequence .control valve 21. This type of valve is of conventional design well known-in the art and will therefore not be disclosed in detail. However, it comprises a valve stem II spring pressed outwardly which normally prevents passage of fluid from the line 26 into a flexible line 32 leading into the upper end of the cylinder II. when said valve stem is pressed inward as indicated in Fig. 1 the fluid may however, flow freely through the valve. The valve ciple of which is well stem is ineffective to prevent a flow in the opposite direction.

Pressure on the lower end of the piston 23a within cylinder 28 causes the piston to move-upward and to rock a three-armed lever 30 connected thereto counter-clockwise about a pin 35 fixed to the aircraft framework, depressing the valve stem 3| of the sequence valve 21 and thus communicating the line 26 with the flexible line 32. Fluid passin through the latter line now holds the piston I8 extended as shown in Fig. 1. The upper end of cylinder 28 is now connected in parallel with a second sequence valve H to a line 40 which is communicated by valve 22 with a line-24 leading to the inlet side of the aforementioned pump or to a reservoir in circuit therewith.

An articulated strut comprising two pivotally connected sections 33-34 is provided, connected at one end. thereof by pin 36 to the cylinder I4 and pivoted at the other end on the aforementioned frame pin 35. As each wheel II moves into its fully extended position, a latch 31 pivoted at 31 on the aircraftframework engages a hook 38 on the section 33 thereby locking the articulated strut in extended position to prevent collapse of the landing gear.

Movement of the valve handle 2I from its full line to its dotted line position communicates the pressure line 23 with the line 40 extending to the upper end of cylinder 28 and the sequence valve 4| while communicating the return line 24 with the line 26 extending to the lower end of cylinder 28 and the valve 21. Consequently,.the piston 28a is forced 'downward, rocking the lever 30 clockwise to close the valve 21 and open valve 4| to transmit fluid from the pressure line 23 to the lowerside of piston I8. Lever 30 is connected by link 33 to.latch 31 whereby the latter is now released from hook 33. Therefore, each oleo unit I3I4 and wheel II will be rocked upward about pivot I until wheel II reaches the dotted line position IIa where it is latched. For this purpose, a second hook I34 is mounted on the upper section 33 of the articulated strut, and as the strut collapses as an incident to the retraction of the-wheel unit the hook I34 is engaged by'a second latch 43 also pivotedon the framework. Latch 43 is connected by link 44 to lever 33 so that clockwise rocking of the latter moves latch 43 to latching position. 'On the other hand, counter-clockwise rocking of lever 36 will disengage latch 43 and move latch 31 to latching position.

Describing now the means for spinning and braking the wheels, embodying the present invention, each wheel II has attached thereto a fluid motor-brake unit, generally indicated at I43 (Figs. 2 to 6, inclusive). In its preferred form, the unit is of the hydraulic gear type, the basic prinknown and used as either. a pump, motor or brake. It is to be'understood,

naled one. stub shaft 43 supported in a casing which encloses both gears I44 and 48. The casing is formed in two sections comprising a base 50a and a cover 53b. The base section 58a is fitted over the hub of wheel II and a lubricant retaining seal H is interposed between the hub and the base to prevent leakage of the bearing lubricant or braking fluid. The cover 58b is securely bolted to the base section by bolts 50 and is tightly fitted over a sleeve 52 mounted on the axle I5, a lubricant retaining device 53 being provided to prevent leakage of lubricant or fluid between the fitted surfaces of the cover and sleeve.

An extension 54 (see alsoFig. 5) is formed on the cover section 53bv and embraces one of the pistons I3 of the oleo assembly 50 as to prevent relative rotation between the motor-brake unit and the oleo assembly when the former exerts a torque in functioning as a brake or motor.

The discharge side of the unit I43 is provided with a brake valve 55 (Figs. 3, 5 and 6) journaled in an extension 56 formed in the base section 53a and extends into a passage 51 communicating the discharge side of the gears I34 and 46 with a flexible discharge tube 58. The valve has a slot 53 (Figs. 3 and 6) therein normally permitting unrestricted passage of fluid through passage 51 while enabling a variable restriction of the passage to be obtained by rotating the valve. The valve 55 has a shank extending through a bushing 60 threaded into the extension 56 and a compression spring 8| is interposed between the valve proper and a bearing ring 33 abutting a sealing ring "53a adjacent the inner end of bushing 60 to normally press the valve 56 longitudinally to lie against a seat 551: formed in the base 50a. The strength of spring 6i may be varied by screwing the bushing 30 in or out, a lock. nut 64 being provided to lock the same in an adjusted position.

' A pilot chamber 65 is formed in the seat 55::

however, that other well known forms of fluid v motor-brake units may be employed without departing from the spirit of the basic aspects of the present invention. 3

Referring to Figs. 3 and 4, each unit I46 comprises a spur gear I44 splined to a connecting sleeve 45 which is rotatably mounted on ball bearings 46 fitted on the wheel axle II. The sleeve 45 is also splined at 41 to the hub of the wheel II thereby forming an integral connection between the wheel and the gear I44 while permitting ready disassembly of these elements.

Gear I44 meshes with a smallergear 48 jourfor the valve 55 and communicates with the passage 51 on the side adjacent the gears I44 and 48 to permit by-passing of the fluid past the-valve under certain conditions to be set forth v hereinafter.

The brake valves 55 are controlled by foot pedals 66 (Fig. 2) which may be of conventional design, being pivotally supported at 61.

Although any desired'control media may be employed I prefer to utilize hydraulic controls comprising actuating cylinders 63, the pistons of which are operated by levers 69 attached to, the pedals 66. Each cylinder 68 is connected by a line 63 to a valve operating cylinder 10 (see also Fig. 5) pivoted at II to the cover 50b of the respective brake unit. The piston I2 of cylinder I3 is normally spring pressed into the position shown in Fig. 5 by a spring I3 interposed between the piston 12 and head of the cylinder. The piston rod 12' is bent at right angles (see Fig. 6)' and is fitted in a bearing formed on a lever 3| attached to the valve 55. Thus, extension of the piston l2 will rock valve 55 causing sequently applies a braking force to the wheels.

In view ofv the fact that any heat generated by the units 40 when acting as brakes may be assaeea 3 dissipated by the hydraulic fluid which y thereafter be cooled by passage through the various lines to be described as well as through a suitable fluid cooler (not shown) if desired, it

be seen that the transmission of excess heat to\ s port of each unit I48 will be communicated with the wheels and tires will be materially reduced.

The construction of each brake valve 88 prevents locking of the wheels in the eventthat the brake pedals are depressed too quickly by permitting by-passing of the fluid past the valves. 18

That is, whenever the pressure built up by the fluid in passing through each unit exceeds a predetermined amount determined by the adjustment of the bushing 88, the fluid in the chamber' 88 presses the valve 55 to the left in Fig. 6 against the spring 8| whereby the fluid may readily pass into the discharge tube 58. The maximum allowable pressure may, for example, be regulated to prevent skidding of the wheels at various speeds.

Means automatically responsive to the extension and retraction of the landing wheels are provided to control the units I48 as either motors or brakes. As diagrammatically illustrated in Fig. 2, the intake port of each unit is connected through a flexible line 15 with a two-way selector valve 18 adapted. to communicate the line 15 with either a braking selector valve I1 or a pump 18. The rotatable elementsof valve 18 are attached td a shaft 88 having an arm 8|, thereon connected to a cable 82. This cable (see Fig. 1) is guided between two sets ofrollers 88 and 88, the former pivoted on studs mounted on the aircraft framework and the latter pivoted on studs extending from the cylinder I4. The lower end of the cable 82 is attached at 88 to the lower extremity of the piston I8. The upper end of the cable is attached to a tension spring 81 tending to raise the cable and thereby rock the shaft 88 and control elements of the valves 18 into their positions illustrated in Fig. 2. However, when the wheels II are extended, and before the aircraft has landed, the wheels will assume positions corresponding to those indicated at IIb, Fig. 1, due to extension of pistons I8, resultingin the cable 82 being lowered against the action of spring 81 to rock the shaft 88, thereby setting the valves 18 to communicate the lines 15 with line 85.

When the aircraft is in normal condition of rest on the ground, which condition is indicated in Figs. 1 and 2, the piston I8 is telescoped into the cylinder I4, as will be noted by comparing the full and dotted lines of Fig. 1. Therefore, spring 81 will hold'the cable 82 in raised position. Suitable ,stop means (not shown) are'provided to hold the shaft 88 from rocking counter-clockwise of its positionillustrated in Fi 2.

The rotatable elements of the braking selector valves 11 are connected to arms 88 normally urged counter-clockwise into their positions illustrated in Fig. 2 by springs 88. .Each of these arms is connected to the piston of a. hydraulic cylinder 88 communicating with the respective brake control lines 88. I The springs 88 are con-j siderably weaker than springs 18 .(Fig. 5) so that application of pressure on the brake lines .88 by the pedals 88 will first result in rocking the respective valve elements 11a of valves 11 from their full line positions shown inFig. 7 to their dotted line positions indicated in that figure, suitable stops (not shown) being provided tollmit the movement of each element 110 in .one or the other of its positions.

which condition is illustrated. in Fig. 1, each of the elements 11a communicates the respective line 81 with a tube 88 which is connected to the top of a vented reservoir 8|, above the fluid level of the reservoir. Therefore, the intake the upper art of reservoir 8 I Consequently the wheels are free to rotate and if any hydraulic fluid remains in the lines 15, 82 and 88 it will be rapidly drained during the first few revolutions of the wheels so that no drag due to forcing the hydraulic fluid throughthe units I48 will be incurred. In this condition of the system the discharge lines 58 are communicated by a lower passage in the elements 11a of valves 11 with a tube 88 leading to the bottom of the reservoir 8|. Consequently, any fluid in the units I48 will be forced into the lines 58 and thence into bottom of the reservoir 8|.

" Upon depression of a brake pedal 88 to brake its associated wheel the associated element 110. will first be set by the. piston of cylinder 88 into its alternate position indicated by the dotted lines of Fig. 7, resulting in fluid from the bottom of the reservoir 8| passing by gravity along line 88 through the upper passage of .element 110, through line 81, valve 18 and line 15 into the intake port 18 of the respective unit I48, enabling the gears of the unit to force the same into the discharge line 58. Also, the lower passage of element 11a. of valve 11 will communicate the line 58 with line 88 leading to the top of reservoir 8|.

Pressure on each pedal 88, after causing valve 11 to be set, results in actuation of the piston 12 of cylinder 18 to rock the respective brake valve 55, thereby restricting the discharge of the brake fluid through the associated unit I48 and consequently braking the wheels II an amount dependent on the depression of the pedals.

Inview of the fact that the valves are located in the units I48 no high fluid pressure is transmitted through any of the hydraulic lines. Further, in'view of the valve action utilized to brake the wheels, the force required to operate the pedals 88 is relatively light.

Describing now the means for operating the 1 wheel units as motors to rotate the wheels prior to landing, so as to drive the same at a peripheral velocity substantially equal to the ground speedof the aircraft, a branch 83a of the line 88 (Fig. 2) connects the reservoir with the intake of the pump 18 while the discharge of the pump is connected through line 85 to each of the selector valves 18. A speed control valve 81 is located in the line 85 and has an arm 88 attached to the shaft 88 thereof. A spring I88 normally holds arm 88 and the rotatable element of the valve 81 in a counter-clockwise position wherein the valve entirely restricts .fluid' in the line 85. Acable I8I (see also Fig. 1) is connected to the arm 88 and is suitably guided by rollers I82 which are mounted on the framework of the aircraft. The lower end of the cable IN is attached to an arm extending from a vane I83 pivotally mounted at IM to one of the cylinders .Il. Whenthe wheels are in extended position, the vane I88 is located below the hull I2 and in the air-stream. Thus, the rate of flow of the fluid through the line 85 may be varied in acconventional design is preferably arranged across the intake and exhaust ports of pump is. The

Whenno pressure is applied to the pedals 88, pump is driven by an electric motor I connected in circuit with a source of power I06. Said circuit is adapted to be closed by a set of switch contacts I 01, I08, the former carried by a bell crank I08a pivotally mounted on the aircraft framework and connected to cable'02.

When the aircraft is in normal condition of flight with the wheels II in their retracted positions Ila (Fig. 1), the arrangement of rollers 84 and 85 relative to each other is such that even though the pistons I3 are extended relative to cylinders I4, the cable 82 will be slack allowing spring 8'! to retain the bell crank I08a and arm in the position shown in Fig. 2 thus holding the motor circuit contacts I01 open. When it is desired to land the aircraft the handle 2I of control valve 22 (Fig. 1) is moved from its current dotted line position to its full line position to extend the wheels to landing position. The wheels will then take up their positions illustrated at b and the cable 82 will be pulled taut by the extended pistons I3, rocking bell crank I08a to close the contacts I01, I08 so as to operate the motor I05. Also, the cable 82 will rock the arm0I to set the valve I6'to communicate line 95 with line I5. Further, valve 9'I'will be opened by air pressure against vane I03 resulting in fluid being forced through lines 95 and 15 into the units I40 to drive the intermeshing gears I44 and 40 whereby to rotate the wheels II. The spring I00 and area of the vane I03 should be so proportioned as to control the speed of the wheels at a rate at least approximately commensurate with the relative velocity between the aircraft and the ground. i

As the plane lands the pistons I3 telescope into the cylinders I4 in performing their shock absorbing functions resulting in the wheels assuming a position substantially as shown in full lines in Fig. 1 thus slackening the cable 82 sufficiently to allow spring 81 to. rock the elements of valves- 16 into the positions shown in Fig. 2 and at the same time opening the contacts I01, I08 to break the motor circuit. Consequently, at this instant the fluid pressure is removed from the intake of the units I40 and the system will assume its free running condition described hereinabove, permitting the aircraft to move freely until it is desired to apply a braking force.

Fig. 8 illustrates an, alternative embodiment of certain aspects of the invention. This arrangement is intended to be used with the conventional form of friction brake or with any other form of brake and comprises an electric motor II 0 pivoted in trunnions extending from brackets I II on the oleo cylinders I4. The motor shaft H2 is connected through an extensible and telescoping coupling II3 with a shaft "4 connected through spiral gears H5 and IIS to the hub of landing wheel II'. From the above it will be seen that a driving connection is maintained by the motor and the wheel irregardless of the relative positions of the piston I3 and cylinder I4 with respect to each other.

.A cable 82, secured at its lower end to a housing I IT for the gears H5 and II 6, is guided between two pairs of rollers H8 and H9 arranged relative to each other in the manner indicated in Fig. 8. The former rollers II8 are rotatably mounted on cylinder w while rollers III! are mounted on the aircraft framework. The upper end of the cable'02' is connected to a bellcrank I20 pivoted on the framework and having a contact I22 formed thereon. A spring I23 normally maintains 'the bell crank in a position to hold contact I22 out of circuit closing engagement with a stationary contact I2 I, these contacts being located in the power circuit I24 of motor Il0.

-When the wheels II are moved into extended position as an incident toa landing operation the extended piston I3 draws cable 82' downwardly against the action of spring I23, thereby closing the contacts I 22 and I23 to energize the wheel spinning motor IIO,.suitable means (not shown) being preferably provided to control the motor at a speed commensurate with the landin speed of the aircraft. As the aircraft lands, the piston I3 telescopes into the cylinder I4, slackening the cable 82' and thereby allowing spring I23 to open the contacts I22 and I23. Ifdesired an over- 5 running clutch may'be provided in the drive between the motor and the wheel to permit the motor to come to rest before the wheel stops.

Referring to Fig. 1 of thepreferred embodiment an auxiliary manual control of the pump 18 may, if desired, be provided to supplant gravity in filling the intake lines with fluid. '1 his control comprises arms I46 and I4! fixed to shafts 80 and 98, respectively, each rockable clockwise by solenoids I41 and I50, respectively, so as to energize the pump motor I05 and effect an open communication between the bottom of reservoir 9| and the intake lines I5. The solenoids are provided in circuit with a source of energy I06 and a switch I48.

Having thus "described the invention, what I claim as new and desire to secure by Letters Patout is:

1. In an aircraft having a landing wheel, and a shock absorber between said wheel and said 5 aircraft, the combination with means for moving said wheel from a retracted position to an extended position relative to said aircraft; of means controlled by said last mentioned means upon operation thereof for rotating said wheel, and means controlled by'said shock absorber upon actuation thereof by said aircraft upon landing for rendering said wheel rotating means ineffective.

2. In an aircraft having a landing wheel, the combination with means for moving said wheel from a retracted position to an extended position relative to said aircraft; of motor driven means controlled by said last mentioned means upon operation thereof for continuously rotating said wheel, and means controlled by the impact between said aircraft and the ground upon landing flor rendering said wheel rotating means ineffecive.

3. In an aircraft having a landing wheel and a shock absorber between said wheel and said aircraft, the combination with means for moving said wheel from a retracted position to an extended position relative to said aircraft; of means controlled by said last mentioned means for rotating said, wheel, means responsive to the forward speed of said aircraft for controlling the speed of said wheel rotating means, and means controlled by said shock absorber upon actuation thereofby said aircraft uPOnJanding for rendering said wheel rotating means ineffective.

4. In an aircraft havinga' landing wheel, and a shock absorber between said wheel and said aircraft, thecombination with means for moving said wheel from a retracted position to an extended position relative to said aircraft; of means including an electric motor for rotating said wheel; an electric power circuit for said motor including a switch; means controlled by'said first mentioned means for closing said switch and 15 means controlled by said shock-absorber upon to act as a motor, means mentioned means upon operation craft; the combination said wheel from I 2,381,842 actuation thereof upon landing for opening said switch.

5. In an aircraft having combination of a fluid motor for rotating said wheel, a fluid power circuit for said motor, a

valve in said power circuit, and means responsive to the air speed of said aircraft for controlling said valve.

6. In an aircraft having a landing wheel and a. shock absorber between said wheel and said aircraft; the combination with means for moving said wheel from a retracted position to an extended position relative to said aircraft, an energy a landing wheel; the

transmitting device operativeiy connected to said wheel, means for controlling said device to operate as a brake, means for controlling said device responsive to said first thereof to cause operation of said last mentioned controlling means, and means responsive to actuation of said shock absorber by said aircraft upon landing for conditioning said first mentioned controlling means to control said device.

'7. In an aircraft having a landing wheel, the combination with means for moving said wheel from retracted position to extended position relative to said aircraft; of an energy transmitting device operatively connected to said wheel and selectively operable as a motor and as a brake, means responsive to said first mentioned means upon operationthereof to condition said device to operate as a motor, and means controlled by the impact between said aircraft and the ground upon landing for conditioning said device to operate as a brake.

8. In an aircraft a shock absorber between said wheel and said airwith means for movin retracted position to extended position relative to said aircraft; of an energy transmitting devicesoperatively connected to said wheel and selectively operable as a motor and as having a landing wheel, and

a brake. means responsive to said first mentioned means upon operation thereof to condition saiddevice to operate as a motor, and means controlled by said shock absorber in response to landing said aircraft for conditioning said device to operate as a brake.

, operate as a motor,

9. In an aircraft having a landing wheel, the

" combination with means for moving said wheel from retracted position to extended position relative to said aircraft; of an energy transmitting device operatively connected to said wheel and selectively operable as a 'motor and as a brake, means responsive to said firstmentioned means upon operation thereof to cause said device to and means controlled by the impact between said aircraft and the ground upon landing for rendering said last mentioned means ineffective andfor conditioning said device to operate as a brake.

10. In an aircraft having a landing wheel the combination with means for moving said wheel from retracted position to extended position relative to said aircraft; of means including a fluid displacement device selectively. operable as a variably restricting said fluid from passing 6 by to cause the same to through said device whereby to cause said device to operate as a brake.

11. In an aircraft having a landing wheel, the combination with means for moving said wheel from retracted position to extended position relative to said aircraft; of means including a hydraulic fluiddi'splacement device selectively operable as a motor and as a brake, means responsive to said first mentioned means upon operation thereof to apply hydraulic fluid under pressure to said device whereby to cause said device to operate as a motor, means responsive to said aircraft upon landing thereof to render said last mentioned means ineffective, a normally inoperative brake lever, and means responsive to said brake lever upon operation thereof for applying fluid to said device and for variably restricting said fluid from passing through said device whereact as a brake. Y

FRED N. scnwsun. 

